I have a box running FreeNAS 0.68 that has been stable for the past year with 2 500 GB arrays in software RAID 1. I had a minor hiccup with the previous version that involved all my mountpoints mysteriously vanishing when I added a new disk but which has not plagued the version I'm currently running.

If you are looking for a simple storage server that is relatively simple to setup then FreeNAS is a way of doing that which is accessible to people who don't have the time/patience/experience for something that is more involved. I wouldn't recommend it's use for a production environment though - I found encryption support wasn't really there and I need a full shell and common applications in my path to get things done quickly and FreeNAS is kind of limited in that respect.

Because one of my chief requirements for a production storage array is encryption I did some reading and eventually settled on OpenBSD - good sources of information, for those interested, are Mark Hoekstra's blog at geektechnique [dot] org and of course openbsd [dot] org/crypto.html.